动态核事故农业后果评估模型开发及应用研究

为了评估核事故对农业生态环境的影响,建立了动态核事故农业后果评估模型AgrRAM(Agriculture radioactivity assessment Model)。AgrRAM基于动态模型理论,从沉积计算开始模拟了放射性核素在农业环境中的动态迁移过程,真实地反映了核事故后农业辐射效应。用AgrRAM模型以田湾核电厂为中心进行200 km×200 km范围的假想事故模拟计算,计算了不同事故时间典型农产品比活度空间分布及时间序列,说明AgrRAM具有动态模拟核事故农业后果的功能。计算结果表明:事故发生时间与农产品的生长特征密切相关,134Cs在不同事故时间农产品中的最终活度变化为1～2个数量级,131I不同事故时间对最终活度的影响达1～5个数量级;相同条件下,农作物中131I的活度水平衰减较快,如果收割时间距事故时间间隔较长,则131I的辐射危害较小。模型参数灵敏度测试显示转移因子对活度水平影响显著,尤其是只有根吸收的作物。模型的可靠性验证分析显示,AgrRAM与保守的平衡模型结果偏差在5倍左右,说明了AgrRAM结果的可靠性。

Development and application of a dynamic model for assessment of agriculture consequences of nuclear accident

In order to evaluate the impact of nuclear accidents on agricultural ecological environment, a dynamic agricultural radiation assessment model(AgrRAM) was developed. Based on the dynamic model theory, AgrRAM simulates the dynamic transfer process of radionuclides in an agricultural environment from the deposition stage, which reflects real agricultural radiation effects after a nuclear accident. Taking Tianwan nuclear power plant as the epicenter, the simulation of hypothetical accidents in the range of 200 km×200 km was carried out by AgrRAM. The spatial distribution and time series of the specific activities of typical agricultural products were calculated to show the function of AgrRAM as dynamically simulating the agricultural consequences of nuclear accidents. The time of the accident was closely related to the growth characteristics of the agricultural products.The different accident time made the specific activity change by 1~2 orders of magnitude for ¹³⁴Cs and 1~5 orders of magnitude for ¹³¹I. Under the same conditions, the activity of ¹³¹I in crops decayed faster than other nuclides, and if the interval between harvest time and accident time was long enough, the radiation damage of ¹³¹I was small. The sensitivity tests of the model parameters showed that the transfer factor had a great influence on the activity, especially for crops with only root uptake. The reliability analysis of AgrRAM showed that the deviation between AgrRAM and the conservative equilibrium model was approximately 5 times, which indicates the reliability of AgrRAM.